Batteries are commonly used as power sources for portable electric devices, such as a mobile phones, laptop computers, tablets, etc. In general, a battery contains a limited capacity, which means that the battery is capable of supplying power for a limited amount of time before the battery needs to be recharged (in the case of rechargeable batteries). Battery monitors are used to monitor the remaining capacity of the battery in order to provide feedback to the operator of the battery-operated device as to how much useful battery life remains for the device.